As electric elements have become common in consumer goods and industrial products formed of various plastics, synthesis fibers, synthesis papers and the like, demand for plastics having antistatic properties as well as antistatic performance such as static electricity-removing property has been increased rapidly.
Those used as such antistatic plastics include ionomer resins.
An ionomer is obtained by partially neutralizing a copolymer of ethylene and an unsaturated carboxylic acid with a metal. As the metal, alkali metals, particularly those containing K, Rb or Cs ion are known to exhibit superior antistatic properties due to ionic conduction thereof. Further, even when such ionomer is not treated with an antistatic agent, the resin itself exhibits conductivity. As a result, such ionomer is known to sustain an antistatic effect semipermanently.
Accordingly, there have been already proposed a number of antistatic materials utilizing an ionomer, molded articles thereof, and their improvements. For example, there is disclosed an antistatic material for polymers which is comprised of an ionomer composition obtained by adding a polyhydric alcohol, such as glycerin or trimethylolpropane, to an ionomer of an ethylene-unsaturated carboxylic acid copolymer whose ion source is an alkali metal such as potassium (for example, see Japanese Patent Application Laid-Open (JP-A) No. 08-134295).
Further, there is disclosed an ionomer composition which is comprised of a mixture containing a component obtained by adding a small amount of a polyhydric alcohol-based compound or an amino alcohol-based compound to a potassium ionomer of an ethylene-unsaturated carboxylic acid copolymer haying a neutralization degree of 60% or more and an ethylene-(meth)acrylate-maleic monoester copolymer at as specific blending ratio, the ionomer composition being non-electrostatic, particularly not showing its humidity-dependency (for example, see JP-A No. 2002-12722).
There is disclosed an injection-molded article of a resin composition containing a potassium ionomer of an ethylene-(meth)acrylic acid random copolymer and as a styrene polymer (for example, see Japanese Patent No. 3565892).
By the way, in recent years, there has been a need for a molded article having electrical performance such as prevention or removal of static electricity as well as optical characteristics such as transparency.
The methacrylic resin typified by poly methyl methacrylate (PMMA) is known as a resin having excellent transparency. There has been a need for improvement in antistatic properties of the resin.